JP2008536059A - High-speed movable bearings especially for supporting the spindle of machine tools - Google Patents

Abstract

According to the present invention, the high-speed movable bearing (1) has a plurality of ball rows (6, 7, 8, 9, 10) provided side by side and the radial heat of the race (2, 3) due to operation. It is configured as a movable ball bearing that automatically compensates for expansion, and the race (2, 3) is in the cold state of the high-speed movable bearing (1), and the rolling surface for the rolling element (4) in the inner race (2) Due to the convex structure of (5), both the races (2, 3) are supported and contacted via only one ball row (8), with both the thermal expansion and centrifugal force expansion of both races (2, 3). ) Is elastically bent in the radial direction, and the other ball rows (6, 7, 9, 10) are sequentially brought into contact with both the races (2, 3), so that the high-speed movable bearing (1 ), The races (2, 3) are in support contact with each other through all the rows (6, 7, 8, 9, 10). Unishi to have.

Description

  The invention relates to a high-speed movable bearing according to the features forming the superordinate concept of claim 1 that can be used to support the spindle of a machine tool or to support other high-speed rotating machine parts.

  It is generally known to those skilled in the art of rolling bearing technology that at least two bearings provided at specific intervals are required to guide and support the rotating machine parts. If the shaft is supported by two radial bearings as usual, the problem arises that the spacing between the bearing seats on the shaft and in the housing only matches within manufacturing tolerances. Furthermore, since the shaft is generally strongly heated by the housing under operating conditions, the length differences due to the temperature of the shaft at the support must also be compensated. Therefore, an effective possibility before compensating for manufacturing tolerances and length differences is that the shaft is guided in the axial direction only in one fixed bearing, and in the other support location by the movable bearing, the inner race fixed location, the outer Different spacings at the race fixing points or at the bearings themselves are compensated by the relative movement of the races. As a fixed bearing of such a bearing device, a deep groove ball bearing, a spherical roller bearing, a tapered roller bearing or a double row or two single row angular contact ball bearings are particularly suitable depending on the required accuracy of the axial guide of the shaft. Although found to be suitable, movable bearings are most easily realized with cylindrical roller bearings or needle bearings. This is because in these types of bearings, it is possible to move the rolling element ring on a raceway or shaft rolling path without a bending edge, respectively.

  However, when using cylindrical roller bearings or needle bearings as the movable bearings of machine tool spindles that are water-cooled, if there is a temperature difference between the inner race and the outer race or between the shaft and the shaft housing, different thermal expansion causes It has been found that these bearings have the disadvantage that they have the high radial stiffness found in the increasing radial clamping of the bearings. This radial tightening due to the temperature increases the radial tightening between the race and the rolling element, and the resulting frictional heat exceeds the allowable operating temperature of the bearing and the required friction between the rolling element and the race. The lubricating film may tear, leading to partial combustion of the lubricant and premature failure of the bearing. A known possibility of avoiding such premature bearing failure is to appropriately preset the radial clearance of the bearing, but this is via a conical seat which is costly for the inner race on the machine tool spindle. Such radial clearance setting is very time consuming and requires a very expensive envelope measuring instrument.

  Another possibility of realizing a movable bearing when supporting the machine tool spindle is the ball bearing disclosed in EP 926368, the outer race having a grooved ball rolling path, and the inner race Is made of ceramic, which is constructed so that it has a flat ball rolling path in the longitudinal section and can be provided between the races. Due to the configuration of the bearing with a given radial clearance, the bearing has sufficient fit on the shaft and in the housing and favorable operating clearance, and the axial movement of the inner race in the range of a flat rolling surface Thus, the movable bearing function can be ensured.

  A ball bearing constructed in this way, due to its predetermined radial clearance, prevents radial thermal expansion of the race due to operation, but has a low load capacity, so the bearing suddenly has a very large point load. In the case of so-called collisions, they tend to damage the material and eventually cause a total failure. Furthermore, in practice, a given radial clearance of the bearing is not sufficient to avoid bearing overload in the case of a large thermal gradient from the inner race to the outer race, so that such a two-row structure bearing itself It is impossible to guarantee a uniform and accurate radial spindle guide in all operating states of the bearing.

  Thus, starting from the above-mentioned drawbacks of the known prior art solutions, the problem underlying the present invention contemplates a high-speed movable bearing, in particular for supporting the spindle of a machine tool, thereby fixing the spindle. In addition to the ability to compensate for differences in length due to spindle temperature relative to the bearing, it avoids race overload resulting from race radial thermal expansion due to operation, in all temperature and operating conditions of the bearing. It is also possible to ensure a uniform and accurate radial spindle guide.

  According to the present invention, the object of the present invention is to provide a high-speed movable bearing according to the superordinate concept of claim 1, wherein the high-speed movable bearing has a plurality of ball rows provided side by side and performs radial thermal expansion of the race due to operation. It is configured as a movable ball bearing that automatically compensates, and the race is supported by a convex structure of the rolling surface for the rolling element in the inner race with only one ball row in the cold state of the high-speed movable bearing. However, as the thermal expansion and centrifugal force expansion of both races increase, the configuration in which one race or both races elastically flexes radially causes the other rows to contact each race in turn. Thus, the races support and come into contact with each other through all the rows of balls at the operating temperature of the high-speed movable bearing.

  In a suitable development, the high-speed movable bearing constructed in accordance with the invention has as many as possible five rows of steel balls or ceramic balls of the same diameter as rolling elements, with only the rolling elements of the central ball row. The high-speed movable bearing is in cold contact with both races in support contact. Providing three ball rows side by side has the advantage that the outer radial load is distributed almost evenly on the individual ball rows and that the bearings are significantly more robust than the entire and known single or double row ball bearings. There is. However, depending on the use case, it is also possible to construct a high-speed movable bearing with less or more than five ball arrays. When choosing materials and shapes for rolling elements, it has been found that the use of ceramic balls is particularly advantageous because the balls can be manufactured more accurately than cylindrical rollers, for example because of their ideal shape. The balls provide a quiet operation of the movable bearing. Furthermore, ceramic balls can be manufactured at a lower cost as compared to balls made of known rolling bearing steel that can be used instead of ceramic cylindrical rollers.

  In order to prevent the movable bearing constituted by such a number of ball rows from requiring a significantly larger axial structure space than the conventional movable bearing, as an advantageous configuration of the high-speed movable bearing constituted by the present invention, The rolling elements of the individual ball trains are provided in a common cage, spaced uniformly from one another in the circumferential direction, so that the axial width of the high-speed movable bearing is equal to that of the five rolling elements in one row. It is suggested to be smaller than the sum of the diameters. In practice, the axial width of the movable bearing constituted by five interlaced ball arrays is almost equal to twice the width of the single-row movable ball bearing described in the prior art, which is present in most uses. It is found that the axial structure space is not adversely affected.

  The intricate arrangement of the ball train is another configuration of the high-speed movable bearing constructed according to the present invention, in which the rolling elements of the central and axially outer ball trains and the rolling elements of both ball trains adjacent to the central ball train are shown. Are provided on the common horizontal axis line that continues alternately in the circumferential direction. At that time, only one bridging piece that divides the ball pocket in the cage is provided between the rolling elements provided on the center and the horizontal axis of the ball row outside in the axial direction, and adjacent to the ball row in the center. The rolling elements that are separated from each other only by the bridging pieces that divide the ball pockets in the cage in the same manner, are arranged between the center and the horizontal axis of the ball line on the outer side in the axial direction, respectively. It is provided at the height of the bridge piece that partitions the ball pocket.

  Furthermore, according to another feature of the high-speed movable bearing constructed according to the present invention, five rolling grooves provided side by side in accordance with the number of ball rows are formed on the inner surface of the outer race formed as flat as possible. It is processed as a guide part. These rolling grooves, which have a radius slightly larger than the rolling element radius for rolling element lubrication, are configured such that their cross-sections have the same width and depth, respectively, and are directly transitioning to each other. Is guided in the rolling groove almost a quarter of its circumference.

  In another configuration of the high-speed movable bearing constructed in accordance with the present invention, a particularly large thermal gradient between the machine tool spindle and the shaft housing, so that both races are preferably elastically deflected radially. Each of which has an annular recess with a concave cross section on its outer surface, these annular recesses extending over almost the entire axial width of the race, the maximum depth of which is approximately equal to half the thickness of the race . These annular recesses on the outer surface of the race thus reduce the material cross-section of the race, which reduces the stiffness of the race towards the center of the axis and at the same time increases the radial elasticity of the race towards the center of the axis. . In doing so, it has been found advantageous to further process the surface of the concave annular recess by precision grinding to avoid race overload failure which in some cases results from a notch effect of surface roughness. On the other hand, the axial edge area of both races following the concave annular recess is formed without precision grinding to flatten again, so that the race can be passed through these edge areas configured as an annular bearing seat. Can be mounted in the shaft housing or on the main shaft without problems. However, in use cases with a significantly large thermal gradient between races, only the outer race or only the inner race can be configured to be elastically elastic in the radial direction as described above. Then the risk of destruction resulting from the notch effect of the surface roughness is eliminated.

  Therefore, the high-speed movable bearing constructed according to the invention, in particular to support the spindle of the machine tool, is due to the temperature due to the special configuration of the race and the configuration of the multi-row ball bearings compared to the rolling bearings known from the prior art. In addition to the ability to compensate for the difference in length of the main spindle relative to the fixed bearing seat, it automatically compensates for race radial thermal expansion and centrifugal expansion due to operation, and thus in any operating and temperature conditions of the bearing. Also has the advantage of being able to guarantee a uniform and accurate spindle guide. Due to the concave design of the rolling surfaces for the rolling elements in the inner race and the appropriate design of the bearing radial clearance, a precise spindle guide in the cold state of the bearing is first supported by the central ball in contact with both races. Guaranteed through the column. Then, due to the thermal expansion of the race due to increased centrifugal force and operation, both ball rows adjacent to the central ball row also support and contact both races. When the high-speed movable bearing constructed in accordance with the present invention finally reaches its operating temperature, the configuration of the race elastically deflected in the radial direction causes both the ball trains on the outside in the axial direction to support and contact both races. In this case, the central ball train is not overloaded and there is sufficient bearing stiffness at any temperature of the bearing. Although the configuration of the high-speed movable bearing configured as a five-row ball bearing according to the present invention causes a slightly larger bearing friction than the known single-row ball bearing, the high-speed suitability of this bearing is maintained. . At the same time, this makes it possible for the inner race of the high-speed movable bearing according to the invention to be significantly less inclined with respect to the outer race, for example compared to a two-row cylindrical roller bearing. Furthermore, the high-speed movable bearing constructed according to the present invention can use a contactless sealing plate to store the lubricant without maintenance, and can be manufactured at low cost instead of expensive ceramic rollers at a low manufacturing cost. Excellent in that ceramic balls are used.

  A preferred embodiment of a high speed movable bearing constructed in accordance with the present invention will be described in detail below with reference to the accompanying drawings.

  FIG. 1 schematically shows a machine tool drive device including an electric motor 26 and a main shaft 27 driven thereby. As can be clearly seen, one end of the main shaft 27 is supported by two angular contact ball bearings 29 and 30 which are configured in a shaft housing 28 as a fixed bearing seat 31. On the other hand, the other end of the main shaft 10 is supported by a movable bearing seat 32 formed by the high-speed movable bearing 1 configured according to the present invention. Therefore, as can be seen from FIG. 2, the high-speed movable bearing 1 is provided between the inner race 2 mounted on the main shaft 27, the outer race 3 mounted in the shaft housing 28, and the races 2 and 3. The inner race 2 for the rolling elements 4 is movable in the axial direction as a movable bearing function including a specific number of rolling elements 4.

  Further, as clearly shown in FIG. 2, the high-speed movable bearing 1 is configured as a movable ball bearing that automatically compensates for the radial thermal expansion of the races 2 and 3 caused by the operation according to the present invention. 4 has five rows of ball balls 6, 7, 8, 9, and 10 provided side by side with ceramic balls of the same diameter. As can be seen only vaguely from FIG. 2, the races 2 and 3 of the high-speed movable bearing 1 have a central configuration due to the convex configuration of the rolling surface 5 for the rolling elements 4 in the inner race 2 when the bearing is cold. Due to the configuration in which the two races 2 and 3 are elastically deflected with increasing thermal expansion and centrifugal force expansion of both races 2 and 3, but only in contact with each other via the ball array 8. The other ball trains 6, 7, 9, 10 are sequentially brought into contact with both races 2, 3, so that at the operating temperature of the high-speed movable bearing 1, the races 2, 3 are connected to all the ball trains 6, 7. , 8, 9, 10 are brought into support contact with each other.

  For this purpose, the rolling elements 4 of the individual ball rows 6, 7, 8, 9 and 10 are also common with a uniform spacing in the circumferential direction, as can be seen only vaguely in the same way from FIG. Since the cage 11 is provided in a complicated manner, the axial width of the high-speed movable bearing 1 is smaller than the sum of the diameters of the five rolling elements 4 in one row. In this case, because of the intricate arrangement of the ball rows 6, 7, 8, 9, and 10, the rolling elements 4 of the ball row 8 at the center and the ball rows 6 and 10 on the outer side in the axial direction are provided on a common horizontal axis. Similarly, the rolling elements 4 of both the ball rows 7 and 9 adjacent to the central ball row 8 are respectively between the horizontal axis of the rolling elements 4 of the center and the axial ball rows 8, 6, 10 in the circumferential direction. They are provided on a common horizontal axis. The axial guides of the ball rows 6, 7, 8, 9, and 10 positioned in the cage 11 between the races 2 and 3 are provided side by side, and the five rolling grooves 13, which are well understood in FIG. 14, 15, 16, 17. These rolling grooves are machined into the flatly formed inner surface 12 of the outer race 3 and have the same width and depth in cross section and are configured to have a radius slightly larger than the radius of the rolling element 4. ing.

  As can also be seen from FIG. 2, both races 2 and 3 of the high-speed movable bearing 1 have annular recesses 20 and 21 with concave cross sections, respectively, due to the configuration of elastically bending in the radial direction. Constructed, these annular recesses extend over almost the entire axial width of the races 2, 3 and their maximum depth is equal to approximately half the thickness of the races 2, 3. These concave annular recesses 20 and 21 on the outer surfaces 18 and 19 of the races 2 and 3 reduce the material cross-section of the races 2 and 3, and this reduction in cross-section makes the races 2 and 3 rigid in the race axial direction. It decreases towards the center and at the same time the radial elasticity of the races 2 and 3 increases towards the center of the race in the axial direction. On the other hand, the axial edge regions 22, 23, 24, 25 following these annular recesses 20, 21 of both races 2, 3 are formed flat, and the races 2, 3 are respectively connected via an annular bearing seat. There is no shaft housing 28 or it is mounted on the main shaft 27.

  1 shows a cross-sectional view of a machine tool drive device having a main shaft supported by a fixed bearing and a high-speed movable bearing according to the present invention.   2 shows an enlarged view of half of the cross section of a high-speed movable bearing constructed in accordance with the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High-speed movable bearing 2 Inner race 3 Outer race 4 Rolling surface 6,7,8,9,10 of rolling element 5 2 Ball array 11 Inner surface 13,14,15,16,17 Rolling groove 18 of cage 12 3 2 outer surface 193 outer surface 20, 21 annular recesses 22, 23 edge range 24, 25 18 edge range 26 motor 27 main shaft 28 shaft housing 29, 30 angular contact ball bearing 31 fixed bearing seat 32 movable bearing seat

Claims (7)

  In particular, an inner race (2) mounted on the main shaft (27), an outer race (3) mounted on the shaft housing (28), and these races (2, 3) for supporting the main shaft of the machine tool. ) To enable the inner race (2) to move in the axial direction within the range of the rolling surface (5) for the rolling element (4) as a movable bearing function. High-speed movable bearing (1) has a plurality of ball rows (6, 7, 8, 9, 10) arranged side by side and automatically performs radial thermal expansion of the race (2, 3) due to operation In the inner race (2) with the race (2, 3) in the cold state of the high-speed movable bearing (1). Due to the convex structure, the support contact is made through only one ball row (8), and both The configuration of one race (2 or 3) or both races (2 and 3) to be elastically flexed in the radial direction along with increased thermal expansion and centrifugal force expansion of the other race (2, 3) The ball train (6, 7, 9, 10) comes into contact with both races (2, 3) in sequence, so that the race (2, 3) is all balls at the operating temperature of the high-speed movable bearing (1). A high-speed movable bearing, characterized in that it is in support and contact with each other via rows (6, 7, 8, 9, 10).   It has 5 ball rows (6, 7, 8, 9, 10) as many as possible with steel balls or ceramic balls of the same diameter as rolling elements (4), and a central ball row (6). 2. The high-speed movable bearing according to claim 1, characterized in that only the rolling elements (4) are in support contact with both races (2, 3) in the cold state of the high-speed movable bearing (1). .   The rolling elements (4) of the individual ball rows (6, 7, 8, 9, 10) are provided in a common cage (11) spaced evenly from one another in the circumferential direction and are therefore arranged at high speed. The high-speed movable bearing according to claim 2, characterized in that the axial width of the movable bearing (1) is smaller than the sum of the diameters of the five rolling elements (4) in one row.   Due to the complicated arrangement of the ball rows (6, 7, 8, 9, 10), the rolling elements (4) of the ball rows (8, 6, 10) at the center and the axially outer side, and the ball rows (8) at the center The rolling elements (4) of both ball rows (7, 9) adjacent to each other are provided on a common horizontal axis line alternately continuing in the circumferential direction, respectively. High-speed movable bearing.   Five rolling grooves (13, 14) arranged side by side on the inner surface (12) formed as flat as possible of the outer race (3) according to the number of ball rows (6, 7, 8, 9, 10). , 15, 16, 17), and the cross-sections of these rolling grooves have the same width and the same depth, and have a radius slightly larger than the radius of the rolling element (4). The high-speed movable bearing according to claim 1, wherein the high-speed movable bearing is provided.   As much as possible, both races (2, 3) are formed so as to have an annular recess (20, 21) with a concave cross section on the outer surface (18, 19), respectively, in order to be elastically bent in the radial direction. These annular recesses extend over substantially the entire axial width of the race (2, 3), the maximum depth of which is equal to approximately half the thickness of the race (2, 3). 5. A high-speed movable bearing according to 5.   The axial edge range (22, 23, 24, 25) of both races (2, 3) following the concave annular recess (20, 21) on the outer surface (18, 19) of the race (2, 3) is flat. The race (2, 3) is formed in the shaft housing (28) or on the main shaft (27) only through these edge areas (22, 23, 24, 25) formed as annular bearing seats. The high-speed movable bearing according to claim 6, wherein the high-speed movable bearing is attached.

Images